Peginterferon alpha and ribavirin treatment for 48 weeks leads to a sustained virological response (SVR) in 40%–50% of subjects infected with hepatitis C virus (HCV) genotype 1 or 4 (G1/4) while treatment for 24 weeks produces SVR in 70%–80% of patients infected with HCV genotype 2 or 3. The variability in response to treatment, especially between patients of different racial groups, suggested that human genetic variability might explain differences in treatment response and led to investigations of the role of host genetics in achieving an SVR.

Genome-wide association studies which examine the association between >500,000 single nucleotide polymorphisms (SNPs) and a disease of interest, have been exceptionally successful in finding SNPs associated with response to hepatitis C treatment. In 2009, 3 groups reported that SNPs located near the gene for interleukin-28B (IL28B) were strongly associated with the likelihood of achieving an SVR with peginterferon + ribavirin treatment.[1–3] IL28B encodes a protein that is also known as interferon lambda-3 (IFN-λ3), a type III interferon. The receptors for interferon alpha, a type I interferon, differ from those for IFN-λ3, but both IFN-λ and IFN-α activate the same intracellular pathway (Jak/STAT), which results in expression of many interferon stimulated genes.[4–6]

SNPs rs12979860 and rs8099917, respectively located 3 and 8 kb upstream of IL28B, were the variants most strongly associated with treatment response in these studies. Among treatment naive G1-infected subjects of European ancestry who were enrolled in the IDEAL study, approximately 69% of those who carried 2 C alleles (C/C) at rs12979860 achieved an SVR compared with 33% of those with the C/T genotype and 27% with genotype T/T.[7] Consistent findings were reported for rs8099917 among Japanese, Australian, and European populations.[2–3] These studies demonstrated that carriage of 2 IL28B favorable alleles strongly, but not fully, predicted SVR, while carriage of 1 or 2 unfavorable alleles did not completely predict failure to respond to treatment. It appears that rs12979860 is more predictive of SVR than rs8099917, especially among people of African ancestry in whom rs8099917 is less polymorphic than rs12979860.[1]

In the current issue of Clinical Gastroenterology and Hepatology, Stättermayer and colleagues performed IL28B genotype testing for rs12979860 and rs8099917 in 682 Austrian subjects (G1 = 372; G2/3 = 208; G4 = 102) who completed treatment with peginterferon and ribavirin and agreed to return for genetic testing.8 They found that subjects infected with G1/4 who carried 2 C alleles at rs12979860 (ie, the most favorable genotype) had a greater decline in HCV ribonucleic acid (RNA) 24 hours after the first injection of interferon than did G1/4-infected subjects who carried a T allele (either C/T or T/T). Similarly, subjects infected with G1/4 who carried rs12979860 C/C were more likely to achieve a rapid virological response (RVR; G1: 38% vs 12%) and SVR (G1: 79% vs 43%) as compared with carriers of the T allele. Among subjects infected with G2/3, rs12979860 C/C carriers had a higher likelihood of RVR (75% vs 53%), but the difference for SVR (81% vs 72%) did not reach statistical significance. IL28B rs12979860 genotype was the strongest pretreatment predictor of SVR, but when the initial response to peginterferon and ribavirin was considered, RVR rather than IL28B genotype was the strongest predictor of SVR in this population. The authors concluded that IL28B genotype influenced the rate of initial viral decline with peginterferon/ribavirin treatment and that IL28B genotype, in conjunction with RVR, might be useful parameters in predicting SVR in G1/4 subjects.

The findings of Stättermayer and coworkers confirm prior reports of IL28B genotype testing among subjects treated with peginterferon + ribavirin. Several investigators have reported that subjects with rs12979860 C/C have a greater initial decline in HCV RNA level and a higher likelihood of achieving RVR and SVR.[1,7,9] Thompson reported that IL28B genotype is the most important pretreatment variable to predict SVR, but IL28B genotype loses importance as a predictor of SVR when RVR is included in a multivariate analysis.[7] Stättermayer confirmed that rs12979860 is more informative than rs8099917 as a pretreatment predictor of SVR among those of European ancestry.[1] In total, studies from Stättermayer and others show a strong association of IL28B genotype with virological response to peginterferon + ribavirin treatment, including the rate of early viral decline and the likelihood of achieving RVR and SVR.

The human genome project promised to introduce an era of personalized medicine, in which genetic testing would be used to predict the likelihood of clinical outcomes, including response to drugs, in individual patients.[10] In 2010 several clinical laboratories announced assays for IL28B rs12979860 genotype. Gastroenterologists now must decide whether to obtain IL28B genotype for their HCV-infected patients and, if so, how to incorporate these results into decisions regarding hepatitis C treatment. IL28B genotype joins a considerable list of pretreatment factors that have been shown to predict the probability of SVR, including HCV genotype, HCV RNA level, severity of liver fibrosis, and racial ancestry. Information on each of these factors can help inform the physician and patient of the likelihood of achieving an SVR, however, none alone is sufficient to guarantee or preclude the possibility of achieving an SVR. Although IL28B genotype alone is insufficient for deciding whether or not a patient is likely to respond to peginterferon and ribavirin, we believe that mathematical clinical prediction models based on IL28B genotype and clinical characteristics may prove useful for predicting SVR. Indeed, among interferon nonresponders who were re-treated with peginterferon + ribavirin in the HALT-C Trial, we have presented "proof of concept" that a model that includes IL28B plus some commonly measured clinical variables (HCV viral load, liver fibrosis score and aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio) has good discrimination and predictive ability for the probability of SVR (O'Brien et al, Hepatology 2010;52:382A [abstract]). If validated, such a model could be used to calculate individually tailored probabilities of achieving an SVR for patients. Clinical prediction models may also be useful for ontreatment predictions of SVR.

The availability of IL28B genotype testing to help predict SVR coincides with another major advance in the treatment of chronic hepatitis C, the introduction of direct-acting antiviral agents (DAAs) that specifically target enzymes critical to HCV replication. At this writing, it appears likely that 2 HCV-specific protease inhibitors, boceprevir and telaprevir, will be approved by the Food and Drug Administration (FDA) in 2011. Data from clinical trials suggest that adding a protease inhibitor to the peginterferon + ribavirin regimen increases the overall SVR rate among treatment naive G1-infected patients to 65%–75% (Bacon et al, Hepatology 2010;52:216 [abstract]; Jacobson et al, Hepatology 2010;52:211 [abstract]). However, adding a viral protease inhibitor to current standard of care is not without additional risks. Patients taking these agents are subject to several potential adverse effects, including anemia and skin rash. Furthermore, patients who fail to achieve SVR on a regimen that includes a protease inhibitor will likely harbor resistant viruses that limit future use of protease inhibitors in that patient. Initial studies suggest that IL28B genotype may be predictive of response to treatment with protease inhibitors, too. Among Japanese patients who received telaprevir + peginterferon + ribavirin, Akuta and colleagues reported an SVR rate of 83% for subjects carrying rs12979860 C/C as compared with 32% among subjects who carried a T allele.[11] If confirmed in other populations, these data suggest that carriers of the less favorable IL28B genotypes will be less likely to respond to triple therapy that includes protease inhibitors and raise the possibility that IL28B genotype-based models may be useful for predicting the likelihood of SVR in response to treatment with peginterferon + ribavirin + protease inhibitors.

Until now, the outcome of treatment for chronic hepatitis C could be broadly classified as either successful (SVR) or futile (nonresponse). The advent of the direct-acting antiviral agent (DAA) era promises to increase the number of patients for whom treatment is successful, but also introduce a third outcome— patients who not only fail treatment, but also harbor resistant viral strains that may compromise future treatment options. Thoughtful incorporation of IL28B genotyping into treatment decision-making may serve to increase the number of patients for whom treatment is successful while minimizing those in whom it is deleterious.

Rapid virological response (RVR) is now considered the strongest predictor of sustained virological response (SVR) in patients with HCV undergoing antiviral treatment, and thus, shorter antiviral treatment for these patients has been suggested. However, no data exist on the predictive value of RVR in HCV carriers with normal ALT values. A total of 137 patients with persistently normal ALT treated with peginterferon alfa 2a and ribavirin were studied. Fifteen patients dropped out early because of side effects, and in 10 patients with HCV-1 treatment was discontinued because of lack of early virological response (EVR). RVR was observed in 68% of the patients (42% patients with HCV-1, 90% HCV-2 and 64% HCV-3). An end-of-treatment response was observed in 86% of the patients (68% HCV-1, 100% HCV-2 and 91% HCV-3). SVR was maintained in 91 patients (46% HCV-1, 97% HCV-2 and 82% HCV-3). Overall, 92% patients with rapid response did obtain HCV eradication vs only 38% of those without rapid response. HCV-1 patients with baseline HCV RNA <400 × 103 IU/mL were more likely to achieve RVR and SVR than those with higher HCV RNA levels. We conclude that patients with genotype 1 and normal ALT who achieve HCV RNA negativity at week 4 may have a higher probability of eradicating their infection. Because of the concomitant favourable demographic and virological features often found in this particular subset of patients, the duration of therapy in these people might be shortened in the case of RVR. Persistently normal alanine aminotransferase levels patients with genotype 2 or 3 have a high chance of achieving SVR, so retesting of HCV RNA during treatment may have no additional practical value in these subjects.

Introduction

Historically, patients with chronic hepatitis C virus (HCV) infection and persistently normal alanine aminotransferase levels (PNALT) have been classified as 'healthy' or 'asymptomatic',[1–3] not thought to progress and thus excluded from antiviral treatment.[4,5] Thus, whether patients with chronic hepatitis C (CHC) and normal ALT should be offered antiviral treatment in clinical practice has been disputed until recently.[6–8] Interferon (IFN) treatment is associated with important side effects and is rather expensive, whereas the risk of progression of the disease in this setting is extremely low.[9–11] For these reasons, the first Consensus Conferences on HCV discouraged treatment in subjects outside clinical trials.[4,5] The introduction of the combination of peginterferon (PEG-IFN) plus ribavirin (RBV) resulted in higher response rates.[8–11] The first multicentric study[12] demonstrated the efficacy and safety of therapy with PEG-IFN a-2a plus RBV also in patients with PNALT; however, in this study, subjects with HCV-1 were treated with a fixed RBV dose lower than that universally recommended for this subset of patients (800 mg/day instead of 1000–1200 mg/day). Simulation studies suggest that sustained virological response (SVR) in HCV-1 patients with PNALT significantly increases when the standard weight-adjusted dose of RBV is administered.[13] More recently, an Italian multicentric study showed higher efficacy of the approved dosage of RBV (1000–1200 mg/day) in patients with HCV-1 and PNALT and excellent sustained responses in those with HCV-2 or 3 infection.[14]

Given the side effects and costs of antiviral therapy, the optimal duration of treatment, and the possibility of treating patients for shorter periods has been evaluated.[15–18] According to the new concept of 'response-guided therapy' (RGT), tailored duration of antiviral therapy with shorter treatment for patients with rapid virological response (RVR) has been suggested, chiefly for patients with HCV-1.[19] Despite several studies on the predictive value of RVR in HCV patients with abnormal ALT levels, no data thus far exist on its predictability of response in patients with persistently normal ALT levels. Thus, we have decided to conduct this multicentric study to assess whether RVR might be predictive of SVR also in this particular subset of patients with HCV and to evaluate the cost effectiveness to determine HCV RNA at 4 weeks in these 'easy-to-treat' subjects.

Patients and Methods

Eligibility and Definition

Hepatitis C virus carriers were defined as having HCV RNA positivity by polymerase chain reaction (PCR) and normal ALT in at least four different occasions 3 months apart over a 12-month period. Exclusion criteria were age <18 years or >70 years, HBsAg or human immunodeficiency virus positivity, previous IFN treatment, serum HCV RNA negativity, history of heavy alcohol abuse, clinical or ultrasound (US) signs of cirrhosis, hepatocellular carcinoma, abnormal ferritin levels, neutropaenia (absolute neutrophil count <1500 cells/mm3), thrombocytopaenia (<100 000 platelets/mm3), anaemia (haemoglobin concentration <12 g/dL in women and <13 g/dL in men) and any abnormality of other liver function tests or routine biochemical tests. Pregnant or lactating women were also excluded. All fertile men and women who participated in the trial were strongly advised to use effective contraception methods during treatment and for 6 months after the end of treatment. All patients reporting contraindications to IFN or RBV treatment and those suffering from significant coexisting medical conditions were excluded from this study. Scarce motivation or refusal to sign informed written consent to treatment was considered exclusion criteria.

Liver biopsy specimens obtained within 6 months before study onset were evaluated using the Metavir classification.[20] Ultrasound-guided liver biopsy was performed using a modified Menghini needle. Formalin-fixed, paraffin-embedded specimens were routinely stained with haematoxylin–eosin and reviewed by local pathologists blinded to clinical and biochemical data.

Liver Stiffness Assessment

Liver stiffness (LS) was evaluated by transient elastography (Fibroscan®, Echosens SA, Paris, France). LS was assessed on the right lobe of the liver, through the intercostal spaces, with the patient in the supine position and the right arm in maximal abduction. Ten validated measures were performed in each patient. The success rate was calculated as the number of validated measures divided by the total number of measures. Results were expressed in kilopascals (kPa). The median value was considered representative of the hepatic stiffness. Only procedures with 10 validated measures and a success rate of at least 60% were considered reliable.

Study Design

All patients received PEG-IFN α-2a 180 μg once weekly plus RBV 800 mg/day for 24 weeks (patients with HCV-2 and HCV-3) or 1000–1200 mg/day for 48 weeks (patients with HCV-1, according to body weight). Stepwise reductions of the dosage of IFN and of RBV were permitted in patients experiencing clinically significant adverse events. The dosage of RBV was reduced in patients showing a decrease in the haemoglobin concentration to <10 g/dL, and treatment was discontinued if the haemoglobin concentrations decreased to <8.5 g/dL despite 4 weeks of treatment with a reduced dosage of the drug. Given the aims of this study, PEG-IFN monotherapy was not allowed. Serum HCV RNA concentration was determined at weeks 4, 12 and 24 in patients infected by genotypes 2 and 3 and at weeks 4, 12, 24, 36 and 48 in patients infected by genotype 1. HCV RNA was further evaluated in all patients 24 weeks after the end of the treatment.

Definition of Virological Responses

Rapid virological response (RVR) was defined as undetectable serum HCV RNA at week 4 of treatment. Early virological response (EVR) was defined as detectable serum HCV RNA at week 4 and either undetectable HCV RNA or >2 log10 decrease in serum HCV RNA level at week 12. End-of-treatment response (EoTR) was defined as the absence of detectable HCV RNA at the end of the treatment, while SVR was defined as the absence of detectable HCV RNA levels at end of the follow-up (24 weeks after the end of the treatment). Relapse (REL) was defined as the reappearance of HCV RNA during the follow-up in subjects with previous EoTR.[21]

Statistical Analysis

Statistical significance was assessed by the Chi-squared test with Yates' and Bonferroni's correction and 95% confidence intervals, analysis of variance (ANOVA) and Student's t-test for independent samples. Logistic regression and analysis of covariance were used to analyse categorical and continuous variables, respectively. A P-value of <0.05 was considered significant. Data are expressed as means ± SD.

Results

One hundred and thirty-seven consecutive patients (102 women, range 19–64 years) referred because of HCV positivity and PNALT to the Liver Units participating in this study were evaluated (see appendix). Fifty-eight of one hundred and thirty-seven patients (42%) had HCV-1, 67 had HCV-2 (49%) and 12 (9%) had HCV-3. The mean serum HCV RNA level was 220 ± 95 × 103 IU/mL (range 1.9–4.800 × 103 IU/mL). Only 35% of the 137 patients in study had a history of previous exposure to blood (transfusion, 16; previous intravenous drug addiction (IVDA), 11; unsafe sex with multiple partners, 4; occupational exposure, 6; unsafe tattooing or piercing, 11). In the other patients, discovery of HCV positivity occurred recently by chance as a result of blood donations, screening for endoscopic or surgical procedures, hospitalizations and screening of relatives of HCV-positive patients. In these patients, the actual duration of HCV infection cannot be evaluated. No differences in demographical, virological and histological features were seen between these patients and those with known risk factors for blood exposure.

Liver histology was available in 115/137 patients: 22 patients (19%) had normal liver, 89 (77%) showed F1 fibrosis, three had F2 fibrosis and one had F3 fibrosis. In the remaining 22 patients, histological data were not available because of refusal to perform biopsy (14 patients) or because of inadequate specimens (eight patients). These patients were offered transient elastography through Fibroscan® before treatment, showing normal or low values of LS in 14/22 patients (mean 3.2 ± 2.0 kPa, range 3.0–6.1 kPa), indicative of F0–F1 fibrosis; six patients had LS indicative of F2 fibrosis (mean 8.2 ± 3.4 kPa, range 7–12 kPa), whereas the latter two patients had higher values of stiffness (13.2 and 14.0 kPa, respectively). No demographical differences were seen between these patients and those undergoing liver biopsy. The main demographical, histological and virological features of the patients are shown in Table 1.

Fifteen patients (8 HCV-1, 6 HCV-2, 1 HCV-3) early dropped out because of side effects or refuse to continue treatment: severe pyrexia (one patient), depression (one patient), refuse to continue treatment (two patients), fatigue and other constitutional symptoms (four patients), private problems (three patients), failed to return (four patients). The mean duration of treatment in this group was 3 weeks (range 1–5 weeks). In these subjects, RVR was not evaluated.

Figure 2.Rates of sustained virological response (SVR) according to presence or absence of Rapid virological response (RVR) in patients with HCV-1.

End-of-treatment response was seen in 105/122 patients (86%): 34/50 of patients with HCV-1 (68%, 21 with RVR and 14 without RVR), all of those harbouring HCV-2 and 10/11 (91%, seven with RVR and three without RVR) of HCV-3 infected subjects were HCV RNA negative at the end of the antiviral treatment (Table 2).

Seventy-six of eighty-three (92%) subjects with RVR (Fig. 1) did obtain SVR vs only 38% of those without RVR (15/39; P < 0.0001). By stratifying SVR rates by genotype and RVR, we found that among patients with HCV-1 SVR was observed in 16/21 (76%) of subjects with RVR and only 7/29 (24%) of those without RVR (χ2 = 4.812, P < 0.02; Fig. 2); in patients with HCV-2, a SVR was achieved in 54/55 patients (98%) with RVR and 5/6 (83%) of those without RVR (χ2 = 0.536, P = 0.46, N.S.; Fig. 3), and in patients with HCV-3, SVR was found in 6/7 (86%) of subjects with RVR and 3/4 (75%) of those without RVR (χ2 = 0.136, P = 0.71, N.S.; Fig. 4).

Figure 3.Rates of sustained virological response (SVR) according to presence or absence of Rapid virological response (RVR) in patients with HCV-2.

Figure 4.Rates of sustained virological response (SVR) according to presence or absence of Rapid virological response (RVR) in patients with HCV-3.

HCV-1 patients with baseline HCV RNA <400 × 103 IU/mL were more likely to achieve RVR and SVR. Among the 40 patients with HCV 1 who had the full treatment course, 22 (55%) had HCV RNA <400 × 103 IU/mL and 18/40 had HCV RNA >400 × 103 IU/mL. RVR was seen in 16/22 of the former (73%) and only 5/18 of the latter (28%; χ2 = 6.320, P = 0.012), although continuation of the treatment did allow SVR in 13/16 (81%) and 3/5 (60%) of the patients, respectively (N.S.) (Table 3).

Forty-four of one hundred and twenty-two patients (36%) had ALT levels below 50% of the ULN (≤20 U/L) and 78 patients had ALT ≥ 20 U/L. However, we found that baseline ALT levels did not influence the rates of RVR and SVR, as no differences were seen between the two groups of patients. Logistic regression analysis was applied to identify predictors of SVR. Factors significantly associated (P < 0.05) with SVR on univariate analysis were lower baseline viral load (<400 × 103 IU/mL), non-1 genotype, female gender, lower BMI (<25 kg/m2) and HCV RNA undetectable at week 4 of treatment. At multivariate analysis, only RVR and non-1 genotype were predictors of SVR.

Safety of the treatment was excellent. Except for the 15 patients in which severe adverse events requiring very early treatment premature withdrawal were seen, in the others 122 subjects who did continue treatment no major side effects were reported. In particular, the appearance of anaemia was observed in 21 out of these 122 patients, but reduction of RBV according to the protocol study was needed in only six patients, three of which failed to have SVR. No signs or symptoms of severe thyroid dysfunction were seen.

In all these 122 subjects, side effects were very mild in severity and not different from those seen among patients with abnormal ALT treated with the same schedules during the same period. The more frequently reported events were mild asthenia, minor depression or irritability, fever following early IFN administrations.

Discussion

It is known that HCV carriers with persistently normal ALT levels overall show demographic and virological features (prevalence of women and non-1 HCV genotypes, younger age, often lean, mild liver damage or even absence of fibrosis) traditionally associated with higher response rates to combined treatment with PEG-IFN plus RBV,[2,22–24] and thus, they might achieve SVR even with shorter than usually recommended treatment periods.[25] Despite several studies have evaluated the ability of RVR to predict SVR in HCV patients with elevated ALT levels,[15–18] no data exist on this topic in subjects with PNALT. Furthermore, previous studies have shown that HCV subjects with PNALT have similar[12,13] or even higher[14] chances of SVR than those with abnormal ALT values, and thus, the identification of early parameters able to predict sustained HCV eradication in this setting is needed to avoid unnecessary prolongation of therapy in this population of 'super-responders'. The main predictive factor up till now identified is represented by the absence of HCV RNA at week 4 of treatment, the so-called RVR.

It has been shown that patients with chronic hepatitis C and persistently normal ALT have similar viral kinetics as those with elevated ALT levels during antiviral therapy.[26]

Recently, it has been reported that a 2 log drop in HCV RNA at day 28 was the best predictor of SVR in patients with HCV-1 infection and PNALT treated with PEG-IFN alpha 2 b plus RBV[27] and that a failure to reduce viral load by 2 logs correctly identified patients with a low (<15%) probability of achieving a SVR.

Our data clearly show that patients with PNALT and HCV RNA negativity after 4 weeks of treatment have higher probability to eradicate their HCV infection than those without RVR and that even HCV-1 patients with RVR have excellent rates of SVR: analysing the rates of SVR by genotype distribution, we found that among patients with RVR, an SVR was achieved in 76% of patients with HCV-1, 98% of HCV-2 and 86% of HCV-3. By contrast, in the absence of RVR, an SVR was observed in 7/29 (24%), 5/6 (83%) and 3/4 (75%) of the three groups of patients, respectively.

Thus, the presence or absence of RVR might have great clinical relevance mainly in patients with HCV-1 type. Indeed, whilst patients with HCV-2 or HCV-3 showed good SVR rates regardless of the presence of RVR, in those with HCV-1 genotype the probability to reach SVR significantly decreased from 76% in patients with RVR to 24% in those without RVR. It means that a 4-week stopping rule policy based on RVR does not seem to be cost effective in patients with PNALT and non-1 genotypes, given the exceedingly high virological responses in this group; by contrast, it could have important consequences for the practical management of HCV-1 patients with normal ALT. In fact, patients infected with HCV genotype 1 who became HCV RNA negative by week 4 were more likely to achieve SVR than those who did not become HCV RNA negative until week 12. However, persistent HCV RNA positivity at week 4 does not justify early stopping of the treatment, as 7 HCV-1 patients without RVR did finally achieve SVR.

Recent data suggest that a baseline level of 400 × 103 IU/mL is the most effective cut-off for a high or low probability to achieve SVR in genotype 1-infected patients.[19] Our findings confirm that low baseline HCV RNA values might influence the probability of reaching SVR in patients with HCV-1: in our series of patients, SVR was seen in 81% of HCV-1 patients with RVR and HCV RNA levels <400 × 103 IU/mL vs 60% of those with RVR but HCV RNA levels >400 × 103 IU/mL, although this trend was not significant. It has been shown that HCV-1 patients with abnormal ALT levels and with low baseline HCV RNA level (<400 × 103 IU/mL) and a RVR, there was no significant difference between 24 and 48 weeks of PEG-IFN plus RBV administration, thus suggesting that 24 weeks of therapy is the appropriate treatment duration in this group.[28] By contrast, ALT baseline levels did not influence the rates of RVR and SVR, according to previous studies[12,14] Recently, it has been demonstrated that HCV-1 patients with low baseline HCV RNA levels (<600 000 IU/mL) and an RVR achieve an SVR rate of up to 90.%[18] Jensen et al.[29] reported that up to 23% of HCV-1 patients treated with PEG-IFN plus RBV achieved RVR, 89% of these reaching SVR after treatment duration of 24 weeks.

The higher than usually SVR rates found in our study in patients with genotype 1 might be explained by several factors, such as the high prevalence of women, the mild degree of liver damage, the relatively low mean age and, last but not the least, the normal BMI values observed in the majority of the patients.

In summary, this is the first study showing that patients with genotype 1 and normal ALT reaching HCV RNA negativity at week 4 might have excellent probability to eradicate their infection. Because of the concomitant favourable demographic and virological features often found in this particular subset of patients, the duration of therapy in patients with PNALT might be shortened in the case of RVR. By contrast, PNALT patients with genotype 2 or 3 in any case have a high chance of achieving SVR, so retesting of HCV RNA during treatment has no practical value in these subjects.[30]

Summary. Chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are the major risk factors for hepatocellular carcinoma (HCC). We examined trends in the incidence of HCC among a population-based cohort of people infected with HBV or HCV. HBV and HCV cases notified to the New South Wales Health Department between 1992 and 2007 were linked to the Central Cancer Registry, Registry of Births, Deaths and Marriages, and National HIV/AIDS Registries. Crude HCC incidence rates were estimated using person-time methodology. Age-standardized incidence rates were calculated using the 2001 Australian population. Trends in incidence were examined using join point regression models. Between 1992 and 2007, 1201 people had a linked HCC record: 556 of those with HBV; 592 with HCV; 45 with HBV/HCV co-infection; and 8 with HIV co-infection. The overall age-standardized HCC incidence rates declined non-significantly from 148.0 (95% confidence intervals (CI) 63.7, 287.4) per 100 000 population in 1995 to 101.2 (95% CI 67.3, 144.6) in 2007 among the HBV monoinfected group and significantly from 151.8 (95% CI 62.4, 299.8) per 100 000 population to 75.3 (95% CI 50.8, 105.5) among the HCV monoinfected group. However, incidence rates in the HCV monoinfected group progressively increased from the period 1992-1997 to 2004-2007 when adjusted for age, sex, and birth cohort, and the total number of cases per annum continued to increase. Despite declines in the age-adjusted incidence rates of HCC over time, the absolute number of cases increased likely due to the ageing cohort and an increasing prevalence of both hepatitis B and C in Australia.

"we estimated that telaprevir induced a four-fold more rapid second-phase viral decline than IFN-based therapy.....Even if resistance was avoided by using an appropriate combination of DAAs, other factors might affect our prediction. First, the ability of IFN-sparing antiviral strategies to reach every viral population residing in the liver or in extrahepatic reservoirs is unknown. Second, the combination of several DAAs might increase toxicity and thus the adherence to treatment. How this may impact treatment duration has only been touched on in this study, and more data are needed to understand how the lack of adherence to treatment may favor the appearance and persistence of resistant virus.

Thus, attainment of SVR in less than 10 weeks in 95% of fully compliant patients would require combination drug regimens (1) that have a genetic barrier high enough so that resistance is avoided, (2) that have high drug penetration into all anatomical sites that contain infected cells, and (3) for which the pharmacokinetics of the drugs in the regimen allow the effectiveness of the regimen against viral production to be maintained at high levels throughout the course of treatment.

In summary, our finding that the second-phase slope increases with the effectiveness of therapy and our expectation that a combination of DAA agents will suppress the growth of drug-resistant variants holds open the promise that more effective therapies that use combinations of DAA agents may, one day, lead to SVR with treatment durations of 2-3 months."

ABSTRACT

Hepatitis C virus (HCV) RNA decay during antiviral therapy is characterized by a rapid first phase, followed by a slower second phase. The current understanding of viral kinetics attributes the magnitude of the first phase of decay to treatment effectiveness, whereas the second phase of decay is attributed to the progressive loss of infected cells. Here, we analyzed data from 44 patients treated with telaprevir, a potent HCV protease inhibitor. Using a viral kinetic model that accounts for the pharmacokinetics of telaprevir, we found the second-phase slope of viral decline to be strongly correlated with treatment effectiveness and to be roughly four-fold more rapid than has been reported with interferon-based therapies. Because telaprevir is not known to increase the death rate of infected cells, our results suggest that the second-phase slope of viral decline is driven not only by the death of infected cells, but may also involve other mechanisms, such as a treatment-effectiveness-dependent degradation of intracellular viral RNA. As a result of the enhanced viral decay caused by the high antiviral effectiveness of telaprevir, we predict that if drug resistance could be avoided by using an appropriate combination of antiviral agents, treatment duration needed to clear HCV might be dramatically shortened. Indeed, we predict that in 95% of fully compliant patients, the last virus particle should be eliminated by week 7 of therapy. If the remaining infected hepatocytes act as a potential reservoir for the renewal of infection, no more than 10 weeks of treatment should be sufficient to clear the infection in 95% of fully compliant patients. However, if patients miss doses, treatment duration would need to be extended.

Chronic hepatitis C virus (HCV) infection has a worldwide prevalence of approximately 3%.1 Achieving a long-term, sustained virologic response (SVR), defined as undetectable HCV RNA in serum 24 weeks after the end of treatment, is the most effective way to prevent disease progression. Currently, treatment outcome with pegylated interferon (PEG-IFN) and ribavirin (RBV) is correlated with HCV genotype, and SVR is only achieved in approximately 50% of patients infected with genotype 1 HCV.

After the initiation of high doses of daily IFN with or without RBV, viral kinetics are characterized in most patients by a biphasic decline, where a rapid initial decline lasting for 1-2 days is followed by a slower, but sustained, second phase of viral decay (Fig. 1), where HCV RNA declines 0.42 log10 IU/mL/week, on average, with high variation among patients (standard deviation, 0.36 log10 IU/mL/week).2, 3 Mathematical modeling of viral kinetics has provided valuable insights for the understanding of the determinants of HCV RNA decay after treatment initiation.4 In particular, it has been proposed that the second phase of viral decline is due to the loss of infected cells, and thus, the high variability in the second phase of viral decline could reflect the variability in the strength of the immune response.2 Although several observations support the possibility that the immune response is involved in the second phase of viral decline,2, 5 no means exists to directly quantify the loss rate of infected cells in vivo, and the predictions made by mathematical modeling remain to be validated. Whatever the mechanisms involved in the second phase of viral decline, its determination is of great interest, because it can ultimately determine the length of time of treatment that needs to be given before all virus and infected cells are expected to be cleared.3

Direct-acting antivirals (DAAs) constitute a new stage in HCV therapy. These drugs inhibit specific HCV enzymes important for viral replication, such as the NS3 protease, and thus allow for a more profound antiviral effect than the current IFN-based therapy. Similar to what was observed with IFN-based therapy, HCV RNA after the initiation of protease-inhibitor therapy was found to decline in a biphasic manner, with, in most patients, a second-phase viral decline larger than 1 log10 IU/mL/week.6-9

In order to gain insights into the faster second-phase decline observed with HCV protease inhibitors, we reanalyzed data from 44 patients treated with telaprevir,6 using a new viral kinetic model that accounts for the changes in drug pharmacokinetics/pharmacodynamics (PK/PD). Using the viral kinetic parameters found in this group of patients as a representative sample of naïve genotype 1 patients under telaprevir therapy, and assuming that drug resistance could be avoided, we estimated the treatment time needed to eliminate all virus and infected cells.

Results

Although both the CE and VE models provided good fits to the data at all drug doses used (Supporting Fig. S1), the VE model yielded significantly better fits when assessed by the Akaike information criterion, which allows one to compare the ability of models with different numbers of parameters to fit experimental data (Table 1). Because the VE model gave better fits, we only discuss results obtained with the VE model.

In principle, model parameters may vary according to treatment group. In particular, the parameters related to treatment effectiveness (e.g., k, ∈1, and ∈2) could be different in the telaprevir plus PEG-IFN, compared to the telaprevir monotherapy, group. However, no significant effect was found for any of the viral dynamic or drug effectiveness parameters (all P values >0.2).

We estimated that the initial treatment effectiveness, ∈1 = 0.974, increased and reached a significantly higher effectiveness, ∈2 = 0.999 (P < 0.0001), after approximately 1 day (Supporting Fig. S2). Furthermore, we estimated that there was a small delay, t0, before drug became effective (see Patients and Methods), which was estimated to have nearly the same value in all the patients: t0 = 0.10 days or 2.4 hours.

As reported previously,6 we found that the mean value of δ was high, compared to what has been reported with IFN-based treatments (Fig. 1). However, our estimate of δ is much lower than what was found using the CE model (mean: 0.58 versus 1.19 day-1 in the CE model). Moreover, our estimated value of δ is similar in monotherapy patients (0.58 day-1) and in patients receiving combination therapy (0.57 day-1), thus resolving the apparent paradox of a slower second-phase decline when PEG-IFN was added to telaprevir that was previously reported.6

Because only the first 3 days of treatment were analyzed, we checked whether our estimates would remain unchanged when including later time points (days 6, 10, and 13) in patients treated with telaprevir plus PEG-IFN and in whom no resistant virus was detected.16 Interestingly, we found no significant differences in this subset of patients in the loss rate of infected cells, δ, as compared to the original data set limited to 3 days of treatment (P = 0.49, t test), and the population parameters remained unchanged.

Because the rate of second-phase viral decline was larger in this study using telaprevir than in previous studies using IFN-based therapies, we asked whether the high effectiveness of telaprevir could play a role. We found that δ was significantly correlated with the final treatment effectiveness, ∈2 (r = 0.79, P < 0.001) (Fig. 2A). Thus, for patients in whom drug effectiveness was higher, not only did the first phase bring viral levels down lower, but also the second-phase slope was larger. Adiwijaya et al.,17 although they did not directly explore a correlation between ∈ and δ, found that allowing δ to increase with the telaprevir effectiveness, acccording to a relationship analogous to that shown in Fig. 2A, resulted in a better fit of their model to patient viral-load data. This finding not only supports the correlation we found, but shows its utility in data analysis.

Next, we asked whether this relationship between second-phase slope and treatment effectiveness was only true for telaprevir or whether it had wider applicability. To assess this, the relationship between drug effectiveness and δ was examined, both for the patients in this study and for patients from earlier studies involving treatment-naïve genotype 1 Caucasian patients receiving a high daily dose of IFN (>10 MIU).2, 3, 18 Recent analyses have demonstrated an association between interleukin (IL)-28B genotype and slopes of viral decline.19 Because the samples used here were not be tested for the IL-28B genotype, we restricted our analysis to Caucasians, for whom the chances to carry the favorable alleles are the highest.19 Combining the data from these studies with that from the telaprevir studies, we encompass a much larger range of drug-effectiveness values. We still find a significant positive correlation (r = 0.78, P < 0.001) between drug effectiveness and δ (Fig. 2B). However, further analyses will be necessary to identify precisely whether polymorphisms in the IL-28B gene may affect the relationship between the first and second phases of viral decay in patients treated with IFN.

Interestingly, the second-phase slope in patients treated with telaprevir is much less variable than what was seen with IFN-based treatment. Because δ almost entirely determines the second phase of viral decline (see Patients and Methods), this finding suggests that duration of therapy needed to eliminate all virus and infected cells might be considerably shortened, as compared to IFN-based therapies. We evaluated empirically the distribution function of the time needed to achieve less than one virion in the extracellular body water (see Patients and Methods). We predict that with full patient compliance, 95% of patients could achieve viral clearance within 7 weeks and 99% within 8 weeks (Fig. 3). This time could be significantly delayed, if all drug doses are not taken. For patients taking three doses a day, we estimated that if 16% of doses are randomly missed (i.e., one every 2 days, on average), the time needed to eradicate the virus in 95 and 99% of patients would increase to 9 and 11 weeks, respectively (Fig. 3). If more drug doses are missed or if the missed doses are clumped together, as in a weekend drug holiday, a longer time to eradication should be anticipated (not shown).

Under treatment, each cell, on average, may generate less than one HCV RNA per day. Furthermore, the clearance rate of virions is much faster than that of cells, and thus when all viruses have been cleared, some infected cells may still be present. If SVR is defined as the time to eliminate all infected cells, SVR could be delayed. Because only HCV RNA is observed, the estimated number of infected cells is based, in part, on the rate of viral production per infected cell under treatment, p(1 - ∈) in Equation 1. Because only the ratio (1 - ∈) of the viral production before and during treatment can be estimated, but not the viral production rate itself (p in Equation 1), we considered the values, p = 10 virions/day and p = 100 virions/day, that cover the range of p values found in a previous study in patients treated with telaprevir.20 With lower rates of viral production per infected cell, p, more infected cells are needed to explain the observed level of viremia in patients and hence the longer the time needed to eradicate the last infected cell. Based on these values of p, 2-3 additional weeks of treatments would be needed in order to eradicate all infected cells (Table 2).

Discussion

Using a new viral kinetic model that allowed for an improved description of the changes in antiviral treatment effectiveness, the second phase of viral decay was found to be very rapid, compared with second phases observed in patients treated with IFN alone, with no differences according to treatment regimen. More precisely, we estimated that telaprevir induced a four-fold more rapid second-phase viral decline than IFN-based therapy.2, 3 Because the current understanding of HCV RNA decay attributes the second phase of viral decline to the loss rate of infected cells, our result suggests that either cell death is enhanced or mechanisms of infected cell loss other than cell death may be operating. Yet, because no elevation in alanine aminotransferase, a surrogate marker of liver cell death, was reported during telaprevir-based therapy, the assumption that the enhanced loss rate of infected cells reflects an elevation in the cell death is unlikely.

The current explanation of HCV RNA decline under therapy comes from studies using moderately potent IFN treatment. In that context, assuming that, after a short delay, the viral production rate per infected cell is reduced under treatment by a constant factor, (1 - ∈), has provided excellent fits to viral kinetic data from a variety of studies. Nevertheless, as a result of their very high pressure on intracellular replication, the new direct antiviral agents might be able to continuously reduce levels of intracellular viral RNA and, consequently, the viral production per infected cell in a treatment-effectiveness-dependent manner. This may also be the case for IFN, if its effectiveness is high enough. Although this remains speculative, some experiments using the replicon system support the suggestion that intracellular viral RNA not only initially declines by the factor (1 - ∈), but then continues to decline under protease inhibitor21 or IFN22 treatment. If the rate of viral production per infected cell is constantly reduced during therapy, the second slope of viral decline may reflect not only the rate of loss of infected cells, but also the rate at which viral production declines in infected cells.23 Hence, the higher chance for attaining SVR observed in patients with an initial rapid viral response24 could not only be due to a better immune response, but also to the progressive elimination of intracellular replication complexes resulting from a more potent antiviral treatment.

No matter what the biological mechanism, the rapid second-phase decline observed with telaprevir suggests that the duration of therapy needed to clear the infection might be considerably shortened, as compared to IFN-based therapies. Based on the extrapolation of the kinetics of decline estimated in our population study, we estimated that eradication of all virus particles could be reached within 7-9 weeks in 95% of patients. If SVR is considered to be achieved when the last infected cell has been cleared, rather than when the last virus is eliminated, an additional 2-3 weeks of therapy may be needed. This estimate is based on the current modeling assumption that the level of viral production under treatment in infected cells is reduced by a constant factor. In the framework of a model considering intracellular viral RNA, the progressive vanishing of viral replicative intermediates could lead to the "curing" of infected cells before infected cells die, which would reduce the time to SVR closer to the estimate, based on the last remaining virus particle. Also, our model is deterministic and thus does not consider explicitly the random nature of each possible event (e.g., cell infection, cell death, and virus clearance). Although an approach that includes the randomness of these processes would more accurately capture the probability distribution function for the time to HCV eradication at the individual level, it would not change the distribution function at the population level, where the law of large numbers applies and which was our primary object of study.

Although Fig. 2 shows a positive correlation between treatment effectiveness and second-phase slope, δ, one should not assume that the second-phase slope would continue to increase as drug combinations become increasingly effective. In principle, at some point, the rate of loss of the infected state would be limited by host cell processes, such as the intrinsic rate at which replication complexes decay, and thus would no longer increase with therapy effectiveness. Also, other viral kinetics studies will be necessary to determine whether the relationship in Fig. 2 is true for other protease inhibitors. The second slope of viral decline has been reported for two other protease inhibitors-TMC-430 and danoprevir-and both studies reported a δ value roughly two times slower.8, 9

Another limitation of our calculation of treatment duration is that we assume no loss of drug effectiveness throughout the course of treatment. With this assumption, the rate of second-phase decline is predicted not to decrease during treatment. Is this assumption reasonable with current therapeutic strategies? Based on the high turnover rate of virus and the high error rate of the HCV RNA-dependent RNA polymerase, it has been predicted that all possible single- and double-virus mutants are present at treatment initiation.20 Thus, to avoid resistance emergence, combination therapy would be needed. Because a single-nucleotide substitution could be sufficient to confer resistance to protease inhibitors, the first treatment strategies that are expected to gain regulatory approval would be based on using a protease inhibitor (telaprevir or boceprevir) in combination with the standard of care (SOC). Because only approximately 50% of genotype 1 patients respond sufficiently strongly to the SOC to attain SVR, approximately 50% of genotype 1 patients treated with the current generation of protease inhibitors and SOC may not have a potent enough regimen to fully suppress the growth of protease-inhibitor resistance variants. This should also be the case in the majority of patients who already have failed prior regimens with SOC. Although resistant virus may not grow rapidly enough to cause viral breakthrough,23 they can slow the second-phase decline, as suggested by the relationship between ∈ and δ in Fig. 2, and hence lead to a need for a longer treatment duration. Consistent with this argument, posttreatment relapse with resistant virus has been seen in patients treated with telaprevir and SOC for 12 weeks.25, 26 Nucleoside polymerase inhibitors present a high genetic barrier to resistance,27 but their antiviral activity has tended, so far, to be much lower than protease inhibitors.27 Using a protease inhibitor and a second DAA constitute the natural next step of anti-HCV treatment strategies. Recent results showed high rates of rapid viral response, with no or low prevalence of resistance emergence for up to 4 weeks when the second DAA was a polymerase inhibitor and up to 12 weeks when the second DAA was an NS5A inhibitor.28-31 However, the fact that a resistance-related viral breakthrough occurred in some patients when SOC agents were not added to these cocktails hints that resistant virus may not be suppressed, but only reduced when two DAAs are used.28, 29, 32 Most likely, to attain SVR in 95% of treatment-compliant patients with a 10-week course of therapy would require treatments with three or more DAAs, including RBV. Clearly, at present, there are no approved regimens that meet our criteria of high potency and a high enough barrier to resistance.

Even if resistance was avoided by using an appropriate combination of DAAs, other factors might affect our prediction. First, the ability of IFN-sparing antiviral strategies to reach every viral population residing in the liver or in extrahepatic reservoirs is unknown. Second, the combination of several DAAs might increase toxicity and thus the adherence to treatment. How this may impact treatment duration has only been touched on in this study, and more data are needed to understand how the lack of adherence to treatment may favor the appearance and persistence of resistant virus.

Thus, attainment of SVR in less than 10 weeks in 95% of fully compliant patients would require combination drug regimens (1) that have a genetic barrier high enough so that resistance is avoided, (2) that have high drug penetration into all anatomical sites that contain infected cells, and (3) for which the pharmacokinetics of the drugs in the regimen allow the effectiveness of the regimen against viral production to be maintained at high levels throughout the course of treatment.

In summary, our finding that the second-phase slope increases with the effectiveness of therapy and our expectation that a combination of DAA agents will suppress the growth of drug-resistant variants holds open the promise that more effective therapies that use combinations of DAA agents may, one day, lead to SVR with treatment durations of 2-3 months.

FRANKLIN LAKES, N.J., July 5, 2011 /PRNewswire/ -- Accredo Health Group Inc., the specialty pharmacy of Medco Health Solutions, Inc. (NYSE: MHS), has developed a unique ability to manage the costs of treating hepatitis C (HCV), while keeping patients adherent to a complex medication regimen for a sometimes lethal disease that can lead to liver cirrhosis and certain cancers. The introduction of two new HCV medications that hold tremendous promise but also add even a greater degree of complexity to treatment will require this "high touch" approach to help increase patient adherence.

Patients must be at least 80-85 percent adherent to therapy for the HCV treatment to be effective, and Accredo has results demonstrating that patients who receive therapy from Accredo's nurses and specialist pharmacists are nearly 10 percent more adherent than those who get their therapy from another provider. Accredo has also been successful in using genotype information to identify patients who may need only 24 weeks of therapy, resulting in drug cost savings up to $13,000.

Accredo's high-touch care model helps educate patients about their treatment and the necessity to adhere to it. This includes patient instruction about using their medications, communicating with doctors about treatment programs and assisting patients to manage side effects. This, in turn, helps to improve patient outcomes and reduce costly hospitalizations or the wastage of expensive medications that are not being properly taken.

As Accredo has improved care for HCV patients, boceprevir and teleprevir will likely improve patients' odds for beating the condition that affects 3.2 million Americans, sparing thousands of patients from liver failure, potential transplants or cancer.

"These new drugs will likely be game-changers for HCV patients, but patients are going to need help adhering to treatment," said Richard Faris, vice president and national practice leader for Medco's Rare and SpecialtyTherapeuticsResourceCenter. "Medco's enhanced clinical oversight and expertise in gene-based medicine enables us to help patients get the right treatment and stay on therapy."

The U.S. Food and Drug Administration (FDA) approved the medications in May to supplement treatments of pegylated interferon and ribavirin in patients with HCV genotype 1, the most common type of the virus. The new treatments improve efficacy to approximately 75 percent from 50 percent when pegylated interferon and ribavirin, the standard of care for HCV since 2001, are used together for 48 weeks. At the same time, the new drugs can shorten the duration of treatment to 24 weeks in most patients. Despite being oral drugs, the new treatments that prevent HCV from replicating add a layer of complexity to an already complex treatment program.

The Accredo Model

The Hepatitis C Therapeutic Resource Center at Accredo has been successful in helping patients, physicians and payers with this difficult therapeutic regimen. Accredo's approach is to maximize clinical effectiveness for patients and benefits plan sponsors by reducing the potential for waste. Failure to properly monitor the therapy, genotype and viral load can cost up to $64,000 in unnecessary drug costs for treating an HCV patient. Pegylated interferons are dosed in precise increments based on a patient's weight.

Patient adherence to these therapies is crucial to achieving a successful course of therapy, but made difficult given their significant side effects and intensive drug regimen. Accredo's Hepatitis C Therapeutic Resource Center services include patient training, preventing drug waste, coordination of care, genetic screening, and patient monitoring and counseling to overcome barriers to treatment adherence.

Hepatitis C and its costs

HCV – and subsequent liver cirrhosis – is the leading cause of liver transplant and it is estimated that 30 percent of the 17,000 people on the liver transplant list are infected with HCV. The initial cost for a liver transplant is $315,000 with follow-up care costing $22,000 annually. HCV is also a leading cause of liver cancer. HCV patients also can have significant co-morbidities that require complex care from specialty pharmacy. For example, in the United States up to 8 percent of those with chronic HCV may be HIV co-infected. Overall, an estimated 6,200 persons with bleeding disorders are affected by HCV, representing 44 percent of all persons with hemophilia and 5 percent of all persons with von Willebrand disease. Persons above the age of 21 have the highest rates of infection, since they were most likely to get human blood products as treatment.

About Medco

Medco Health Solutions, Inc. (NYSE: MHS) is pioneering the world's most advanced pharmacy® and its clinical research and innovations are part of Medco making medicine smarter™ for more than 65 million members.

With more than 24,000 employees worldwide dedicated to improving patient health and reducing costs for a wide range of public and private sector clients, and 2010 revenues of $66 billion, Medco ranks 34th on the 2011 Fortune 500 list and is named among the world's most innovative, most admired and most trustworthy companies. Accredo Health Group, Inc., is a wholly-owned subsidiary of Medco.

This press release contains "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995. These statements involve risks and uncertainties that may cause results to differ materially from those set forth in the statements. No forward-looking statement can be guaranteed, and actual results may differ materially from those projected. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Forward-looking statements are not historical facts, but rather are based on current expectations, estimates, assumptions and projections about the business and future financial results of the pharmacy benefit management ("PBM") and specialty pharmacy industries, and other legal, regulatory and economic developments.

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